If congress has the power to declare and fund war, why do people say they have no right to try to stop it?

ie: "It's hard to imagine a more cynical political strategy than trying to hold hostage funding for our troops in combat" GW Bush (source: a href="http://www.whitehouse.gov/news/releases/2007/10/20071030.html)" rel="nofollow"http://www.whitehouse.gov/news/releases/…/a